ECONOMIC THRESHOLDS AND RESPONSE TO UNCERTAINTY IN WEED-CONTROL

The influence of uncertainty on economic thresholds/critical density models in weed control is examined. Two principal sources of uncertainty, potential weed density and the form of the crop loss function, are discussed. A range of criteria including maximisation of net gain, minimax gain and mean-risk analysis are considered in relation to the decision to control or not control weeds in a crop. A notional example of wild oats in wheat illustrates how the various decision criteria can also be considered as thresholds. If risk aversion is present, uncertainty about the weed loss function and weed densities increases the likelihood that control of weeds is optimal and specific threshold weed densities become less relevant.